Cardiovascular Disease and Breast Cancer Stage at Diagnosis.

Importance: Cardiovascular disease (CVD) and cancer are the leading causes of mortality in the US. Large-scale population-based and mechanistic studies support a direct effect of CVD on accelerated tumor growth and spread, specifically in breast cancer. Objective: To assess whether individuals presenting with advanced breast cancers are more likely to have prevalent CVD compared with those with early-stage breast cancers at the time of diagnosis. Design, Setting, and Participants: This population-based case-control study used data from the Surveillance, Epidemiology, and End Results-Medicare linked databases from 2009 to 2020. The analysis was completed from May 2023 to August 2024. Participants were female patients aged at least 66 years diagnosed with invasive breast cancer. Cases were matched with controls by breast cancer stage at diagnosis and propensity scores using factors known to be associated with delayed cancer diagnosis. Exposure: Prevalent CVD prior to breast cancer diagnosis. Main Outcomes and Measures: The outcome of interest was the odds of locally advanced (T3-4 or N+) or metastatic (M+) breast cancer status at diagnosis. Results: The full analytic cohort included 19 292 matched individuals, with median (IQR) age 73 (70-79) years, of whom 1676 (8.7%) were Black and 16 681 (86.5%) were White; 9478 individuals (49.1%) had prevalent CVD. Propensity score-matched, multivariable-adjusted models found that individuals with locally advanced or metastatic breast cancer at diagnosis had statistically significantly increased odds of prevalent CVD (odds ratio [OR], 1.10; 95% CI, 1.03-1.17; P = .007). This association was observed among hormone receptor-positive (OR, 1.11; 95% CI, 1.03-1.19; P = .006) but not hormone receptor-negative (OR, 1.02; 95% CI, 0.86-1.21; P = .83) breast cancer. ORs were directionally consistent when separately examining locally advanced (OR, 1.09; 95% CI, 1.02-1.17; P = .02) and metastatic (OR, 1.20; 95% CI, 0.94-1.54; P = .15) disease, among all receptor subtypes. Conclusions and Relevance: This case-control study found that individuals with more advanced breast cancer at diagnosis were more likely to have prevalent CVD. This finding may be specific to hormone receptor-positive and ERBB2-negative (formerly HER2) disease. Future studies are needed to confirm these findings and investigate interventions to improve patient outcomes, including personalized cancer screening.